<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>圆角</title>
    <style>
        div{
            width:200px;
            height:200px;
            background-color:aqua;
            border-radius:100px;
            margin-bottom: 50px;
        }
        button{
            width:200px;
            height:100px;
            background-color:lightgreen;
            border-top-left-radius:50px;
            border-bottom-right-radius:50px;
        }
    </style>
</head>
<body>
<div></div>
<button>提交</button>
</body>
</html>